How Latex is made

How Latex is Made

Natural: Dipped goods (medical and surgical items, household and industrial gloves, boots, and balloons) utilize more than half of all natural latex consumed in the United States. The adhesives industry is the second largest user of natural latex in products such as shoes, envelopes, labels, and pressure sensitive tape.

Natural latex with a high solids content is also used for making molds for casting plaster, cement, wax, low temperature metals, and limited run polyester articles. Natural latex has the ability to shrink around the object to be reproduced, so that the smallest detail will be reproduced in the cast. Latex is even being used to help stabilize desert soils to make them suitable for agricultural uses.

Synthetic: Most synthetic rubber is created from two materials, styrene and butadiene. Both are currently obtained from petroleum. Over a billion pounds (454,000,000 kg)of this type of rubber was manufactured in the United States in 1992. Other synthetic rubbers are made from specialty materials for chemical and temperature resistant applications.

Raw Materials: The composition of latex sap consists of 30-40% rubber particles, 55-65% water, and small amounts of protein, sterol glycosides, resins, ash, and sugars. Rubber has high elasticity and a polymer molecular structure. This structure consists of a long chain made up of tens of thousands of smaller units, called monomers, strung together. Each monomer unit has a molecular size comparable with that of a simple substance such as sugar. Other special chemicals are used as preservatives or stimulants during the harvesting process.

The Manufacturing Process:
Growing and processing natural rubber is one of the most complex agricultural industries and requires several years. It combines botany, chemistry, and sophisticated machinery with dexterous skills of the people who harvest the trees. Contrast this with synthetic rubber production, which involves chemical reactions and sophisticated chemical processing machinery that is automatically controlled by computers. The production of natural latex is described below.

Seeds from high-grade trees are planted and allowed to grow for about 12 to 18 months in the nursery before a new bud is grafted to the seedling. After bud grafting, the year-old seedling tree is cut back and is ready for transplanting. The bud sprouts shortly after transplanting, resulting in a new tree with better properties.

Tapping: To harvest latex, a worker shaves off a slanted strip of bark halfway around the tree and about one third in (0.84 cm) deep. Precise skill is required for if the tree is cut too deeply, the tree will be irreparably damaged. The latex then bleeds out of the severed vessels, flows down along the cut until it reaches a spout, and finally drops into a collection cup that will later be drained.

A tapper first collects the cut lump, which is coagulated latex in the cup, and tree lace, which is latex coagulated along the old cut. Next, the tapper makes a new cut. The latex first flows rapidly, then declines to a steady rate for a few hours, after which it slows again. By the next day, the flow has nearly stopped as the severed vessel becomes plugged by coagulated latex.

Producing dry stock:
A giant extrusion dryer that can produce up to 4,000 lbs (1,816 kg) per hour removes the water, creating a crumb-like material. The dried rubber is then compacted into bales and crated for shipment.

Forming sheets:
The acid makes rubber particles bunch together above the watery serum in which they are suspended. After several hours, roughly one pound (0.45 kg) of soft, gelatinous rubber coagulates for every three pounds (1.35 kg) of latex.

Producing other products:
To make rubber products, the mix is shaped by placing it in a heated mold, which helps shape and vulcanize the material. For more complex products, such as tires, a number of components are made, some with fiber or steel-cord reinforcement, which are then joined together.

Quality Control: A number of quality checks are made after the latex is harvested. The latex is checked for purity and other properties. After each step of the production process, technicians check physical properties and chemical composition, using a variety of analytical equipment.

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